Symptoms and causes

Symptoms

High body temperature. A core body temperature of 104 F (40 C) or higher, obtained with a rectal thermometer, is the main sign of heatstroke.

Altered mental state or behavior. Confusion, agitation, slurred speech, irritability, delirium, seizures and coma can all result from heatstroke.

Alteration in sweating. In heatstroke brought on by hot weather, your skin will feel hot and dry to the touch. However, in heatstroke brought on by strenuous exercise, your skin may feel dry or slightly moist.

When to see a doctor

If you think a person may be experiencing heatstroke, seek immediate medical help. Call 911 or your local emergency services number.

Take immediate action to cool the overheated person while waiting for emergency treatment.

Get the person into shade or indoors.

Remove excess clothing.

Cool the person with whatever means available — put in a cool tub of water or a cool shower, spray with a garden hose, sponge with cool water, fan while misting with cool water, or place ice packs or cold, wet towels on the person's head, neck, armpits and groin.

Causes

Heatstroke can occur as a result of:

Exposure to a hot environment. In a type of heatstroke, called nonexertional (classic) heatstroke, being in a hot environment leads to a rise in core body temperature. This type of heatstroke typically occurs after exposure to hot, humid weather, especially for prolonged periods. It occurs most often in older adults and in people with chronic illness.

Strenuous activity. Exertional heatstroke is caused by an increase in core body temperature brought on by intense physical activity in hot weather. Anyone exercising or working in hot weather can get exertional heatstroke, but it's most likely to occur if you're not used to high temperatures.

Becoming dehydrated by not drinking enough water to replenish fluids lost through sweating

Risk factors

Anyone can develop heatstroke, but several factors increase your risk:

Age. Your ability to cope with extreme heat depends on the strength of your central nervous system. In the very young, the central nervous system is not fully developed, and in adults over 65, the central nervous system begins to deteriorate, which makes your body less able to cope with changes in body temperature. Both age groups usually have difficulty remaining hydrated, which also increases risk.

Exertion in hot weather. Military training and participating in sports, such as football or long-distance running events, in hot weather are among the situations that can lead to heatstroke.

Sudden exposure to hot weather. You may be more susceptible to heat-related illness if you're exposed to a sudden increase in temperature, such as during an early-summer heat wave or travel to a hotter climate. Limit activity for at least several days to allow yourself to acclimate to the change. However, you may still have an increased risk of heatstroke until you've experienced several weeks of higher temperatures.

A lack of air conditioning. Fans may make you feel better, but during sustained hot weather, air conditioning is the most effective way to cool down and lower humidity.

Stimulants for attention-deficit/hyperactivity disorder (ADHD) and illegal stimulants such as amphetamines and cocaine also make you more vulnerable to heatstroke.

Certain health conditions. Certain chronic illnesses, such as heart or lung disease, might increase your risk of heatstroke. So can being obese, being sedentary and having a history of previous heatstroke.

Complications

Heatstroke can result in a number of complications, depending on how long the body temperature is high. Severe complications include:

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